As mentioned, 新た is more specifically an adjectival noun, which is also what all na-adjectives are. It can be used to function grammatically as a noun, but it’s more common for 新た to be seen in its adjective form (新たな + noun) or being used as an adverb (新たに + ____)

Example of it being used as a noun:

すべてのものは日に日に新たです。

Syntactically, it’s being used as a noun here (noun + copulaです)

From a linguistic standpoint, 新た (and adjectival nouns alike) are a type of noun classified as what’s called a nominal, which means that when acting attributively to describe other words, it takes on a 〜な suffix instead of a 〜の suffix like regular nouns would. (Ex: 新たな発見 vs. 旅の発見)

It’s also interesting to note that 〜な is an abbreviation of 〜にある, which is what is being used to make these types of nouns attributive

In summary, yes 新た is a type of noun known as an adjectival noun, but for this word specifically, it’s less likely to be seen being used as a noun and more likely to be seen as an adjective or adverb ^^